Cost-effective sintered reaction-bonded silicon nitride (SRBSN) for structural ceramics

摘要

Sintered silicon nitride has many superior properties; however, for most applications these materials are too expensive to compete with metal parts. Sintered reaction-bonded silicon nitride (SRBSN) is more economical, with raw materials costs <20% those of comparable high- purity materials, making it competitive with metal parts. Conventional processing of SRBSN requires long nitridation times and a two-step firing process. Microwave (MW) heating reduces the reaction times and is performed in a one-step process, thereby simplifying the operation. The mechanical properties of the MW-SRBSN are not equal to those from the higher-cost powders, but are appropriate for a number of applications at lower temperatures and stress levels. At ambient temperature, typical strength, toughness (K(sub Ic) and hardness values are 480 MPa, 4.8 MPa(radical)m, and 14 GPa, respectively.